Consolidated Balance Sheets (USD $) In Thousands, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011	Jun. 30, 2011
Current assets:
Cash and cash equivalents	$ 4,002	$ 5,833	$ 3,700
Restricted cash	0	0	925
Accounts receivable	13,459	77,449	39,104
Accrued unbilled revenue	12,921	61,925	15,031
Allowance for uncollectible accounts	(2,653)	(2,895)	(2,824)
Regulatory assets	65,297	94,673	59,766
Derivative instruments	2,142	2,853	4,433
Inventories	68,868	74,363	71,229
Gas reserves	11,021	4,463	749
Income taxes receivable	3,119	7,045	26,285
Other current assets	8,606	22,980	9,496
Total current assets	186,782	348,689	227,894
Non-current assets:
Property, plant and equipment	2,720,037	2,661,102	2,612,147
Less: Accumulated depreciation	791,021	767,226	744,929
Total property, plant and equipment - net	1,929,016	1,893,876	1,867,218
Gas reserves	65,026	47,451	15,403
Regulatory assets	366,981	371,392	326,081
Derivative instruments	1,170	0	1,042
Other investments	68,230	68,263	68,576
Restricted cash	4,000	4,000	0
Other non-current assets	13,936	12,903	15,780
Total non-current assets	2,448,359	2,397,885	2,294,100
Total assets	2,635,141	2,746,574	2,521,994
Capitalization:
Common stock - no par value; authorized 100,000 shares; issued and outstanding 26,827, 26,673 and 26,756 at June 30, 2012 and 2011, and December 31, 2011, respectively	352,955	348,383	344,451
Retained earnings	392,082	373,905	376,489
Accumulated other comprehensive income (loss)	(7,467)	(7,800)	(6,312)
Total common stock equity	737,570	714,488	714,628
Long-term debt	641,700	641,700	551,700
Total capitalization	1,379,270	1,356,188	1,266,328
Current liabilities:
Short-term debt	113,200	141,600	185,400
Current maturities of long-term debt	0	40,000	40,000
Accounts payable	48,361	86,300	54,148
Taxes accrued	5,205	10,747	6,805
Interest accrued	5,607	5,857	5,127
Regulatory liabilities	20,748	31,046	25,784
Derivative instruments	29,407	57,317	25,986
Other current liabilities	42,336	41,597	37,574
Total current liabilities	264,864	414,464	380,824
Deferred credits and other non-current liabilities:
Deferred tax liabilities	440,073	413,209	398,825
Regulatory liabilities	280,295	278,382	265,703
Pension and other postretirement benefit liabilities	185,844	201,530	130,985
Derivative instruments	2,130	6,536	9,202
Other non-current liabilities	82,665	76,265	70,127
Total deferred credits and other non-current liabilities	991,007	975,922	874,842
Commitments and contingencies (see Note 13)	0	0	0
Total capitalization and liabilities	$ 2,635,141	$ 2,746,574	$ 2,521,994